Reluctant dieters often dream of being able to eat whatever they want at dinner without gaining weight.

Now one health writer claims he can make the dream a reality – but only by imposing a strict vegan diet during the day.

Mark Bittman has gained thousands of followers in the US with his VB6 diet, which stands for Vegan Before 6pm.

Virtue: A new diet encourages people to eat only vegan food during the daytime in order to lose weight

Eat only vegetables all day, he says, and the kitchen’s your oyster come sunset.

Whether you crave steak, a cheeseburger or a rich chocolate mousse, nothing is barred as long as it is eaten in moderation.

Mr Bittman, 63, claims it helped him lose 15 per cent of his body weight and saved him from developing diabetes. Now the craze is taking off in the UK after his best-selling book was published here this summer.

Vegans eat no animal products, basing their meals on healthy fruit, vegetables and grains, which are high in fibre and nutrients.

Reward: The plan allows dieters to chow down on meat after six o'clock every evening

Mr Bittman describes his ‘flexitarian’ – or semi-vegetarian – plan as a compromise for those who want to be healthy but can’t face giving up the animal foods they love, which are often high in saturated fat.

The author, a food writer for 30 years, adopted the diet seven years ago after doctors said he was pre-diabetic. With high cholesterol and blood sugar, he was told to cut out unhealthy foods or go on medication.

He said: ‘It was the best compromise I could come up with between an all-plant diet and eating the way I was eating.

‘The strategy is common sense. If there’s one or two things that science has found in the last few decades, it’s eat more plants and less junk – this is one way of doing that.’

Mr Bittman said it helped him lose 1st in a month and 1st 7lb in the next few months.

His book, with 60 vegan recipes for lunch and breakfast, topped the New York Times How-To bestseller book list in the US.

Unlike other diets, which promise fast results, he emphasises it is not a ‘quick-fix’ option.

He said: ‘This is a life-long plan. You don’t just do it for three months and give it up. It’s about eating in a way that’s better for you. Many people are overweight and are eating way too much meat and this is a strategy for changing that.’

Eating less saturated fat can reduce the risk of obesity, heart disease and diabetes.

‘But there’s a slight problem in eating animal products in the evening. It makes more sense to have a big breakfast with eggs and bacon and then go down to vegetables for lunch and dinner. Breakfast is very important as your body needs a kick-start at the beginning of the day.’